Method and Apparatus for Producing Staple Fibers

ABSTRACT

A method and an apparatus for producing staple fibers, wherein in a first step a tow is formed from melt spun filaments and deposited into a can, and wherein in a second process step the tows of a plurality of cans in a can creel are withdrawn, treated, and cut to staple fibers. To obtain as much as possible short times of interruption between the first and second process steps, the invention provides for depositing the tow in the first process step directly into the can accommodated in the can creel, with the cans of the can creel being filled one after the other.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of international application PCT/EP2005/001382, filed 11 Feb. 2005, and which designates the U.S. The disclosure of the referenced application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of producing staple fibers from melt spun filaments, as well as an apparatus for carrying out the method.

Basically, two different methods and apparatus are known for producing staple fibers. In a first method and apparatus, the staple fibers are produced in a two-step process. To this end, a plurality of filaments are spun from a polymer melt in a first step, and combined to a tow after cooling. At the end of the first process step, the tow is deposited in a can. In a second process step, a plurality of tows are withdrawn by a treatment unit from a plurality of cans that are accommodated in a can creel. The tows are joined to form one combined tow, which is treated, and finally cut to staple fibers. Such two-step processes are used in particular for processing very coarse total deniers, such as, for example, greater than 200,000 deniers. The invention is related to such method and apparatus.

In the two-step process, it is important that the tows be temporarily stored between the first process step and the second process step, since it is common practice to join in the treatment unit a plurality of tows produced in a first spinning process to a combined tow, and to further process the latter. For the, temporary storage of the spun tows, cans are provided that are reciprocated by costly transportation devices between the spin unit and a can creel associated with the treatment unit. To ensure that the can creel has a supply of cans for carrying out the second process step, a can magazine is provided that temporarily stores previously filled cans. The known methods and apparatus for producing staple fibers in two process steps thus require a great deal of coordination as well as costly transportation devices and a large-surface installation space.

In comparison therewith, methods and apparatus are known, wherein the staple fibers are produced in a one-step process. In this process, the spinning, drawing, crimping, and cutting steps of a tow follow one another directly. However, such methods basically have the disadvantage of small production outputs, since both the withdrawal of the tow from the spin unit and the drawing of the tow must essentially be performed by the treatment unit. In particular in the case of coarser total deniers of the tows, irregularities in the physical properties of the fibers become very noticeable.

It is therefore an object of the invention to provide a method and an apparatus for producing staple fibers in a two-step process, which permit storing and making available tows in the transition from the first process step to the second process step in a simple way with simple means.

A further object of the invention is to further develop the known method and the known apparatus such that they permit further processing the freshly spun tow to the end product with as little time of interruption as possible.

SUMMARY OF THE INVENTION

The above and other objects and advantages of the invention are achieved by a method and apparatus wherein melt spun filaments are formed into a tow, which is successively deposited into each of a plurality of cans accommodated in a can creel. The tow is then withdrawn from the cans and treated and cut.

The invention distinguishes itself essentially in that it does not require costly auxiliary devices for transporting the cans to the spin units. In the first process step, the invention provides for depositing the tow directly into a can that is accommodated in a can creel. The interaction of the spin unit and the can creel permits designing in an advantageous manner a compact combined production line, in which the can creel represents a common interface between the spin unit and the treatment unit.

To enable as much as possible a continuous process sequence, the further developments of the invention are especially advantageous, which provide next to a first can creel a second can creel with a plurality of cans. Thus, for example an advantageous variant of the method makes it possible to deposit the tow in the first process step into the cans of the first creel, while at the same time, in the second process step, the tows are withdrawn from the cans of the second creel.

In this connection, it is possible to achieve an almost continuous operation in such a manner that the cans of the first can creel and the cans of the second can creel are alternately filled with the tow, and that the tows are alternately removed from the cans of the second creel and from the cans of the first creel. In particular in the second process step, this results in very short interruption times, since an exchange of the cans in the can creel is omitted. To continue the process, it is necessary to change only the can creels, which can be realized in very short times.

For purposes of filling the cans accommodated in a can creel in any position, the spin unit includes in accordance with an advantageous further development of the invention, a movable depositing device that is supported and guided by guide means above the creel. With that, it is possible to deposit the tow in any desired position of the can creel into a can accommodated therein.

The tow may be deposited both by an oscillating movement that is imparted to the depositing device, or by an oscillating movement that is imparted to the can accommodated in the can creel. This ensures a high degree of filling with a corresponding filling density.

However, it is preferred to generate the oscillating movement of the tow by the depositing device or by a conveying means that is mounted for movement to the depositing device.

An especially advantageous further development of the apparatus according to the invention provides for associating the depositing device to a feed system, which advances the tow after withdrawing it from the spinnerets. This further development is especially advantageous for being able to fill can creels with a large number of cans and the therewith connected great travel distances with the tow under an adequate tension. In this connection, the feed system associated to the depositing device is used for building up a tensile force.

To make the apparatus as compact as possible for carrying out the two-step process, a preferred further development of the invention provides for arranging the spinnerets and the withdrawal systems of the spin unit above the can creel. This arrangement permits mounting the spinnerets in a centered or offset relationship with the can creel. With the arrangement in tiers it becomes possible to keep the deflections small that are needed for depositing the tow.

The further development of the invention, which provides for associating to each can in the can creel a withdrawal guide element that is adapted for moving between an idle position and an operating position, is especially advantageous for permitting on the one hand an uninterrupted removal of the tows from the cans, and on the other hand for making available a full opening cross section of the cans for filling.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the method and apparatus of the invention are further described in greater detail by reference to an embodiment of the invention as illustrated in the attached drawings, in which:

FIG. 1 is a schematic top view of a layout of the apparatus according to the invention;

FIG. 2 is a side elevation view of the apparatus showing the apparatus in somewhat greater detail;

FIG. 3 is a front elevation view of the can creels of the apparatus; and

FIG. 4 is a top view of the can creels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus as illustrated in FIG. 1 comprises a spin unit 1, two can creels 2.1 and 2.2 cooperating with the spin unit 1, as well as a treatment unit 3. The spin unit 1 includes a plurality of spinning positions for melt spinning a plurality of filaments, which are joined to a tow 11 by means of a withdrawal system 9. Via the withdrawal system 9, the tow advances to a depositing device 10 that is arranged for being positioned above the can creels 2.1 and 2.2.

The can creels 2.1 and 2.2 each accommodate a plurality of cans 13. In the arrangement illustrated in FIG. 1, the depositing device 10 is associated with the can creel 2.1, and in the process of filling a first can 13 of the creel. The depositing device 10 can be moved to each can of the can creel 2.1 for successively filling the cans 13 of the creel 2.1 with the tow.

The cans 13 accommodated in can creel 2.2 are already filled. The tows of the cans 13 of can creel 2.2 are jointly withdrawn by the treatment unit 3 and combined to one tow 14. To this end, a plurality of guide rolls 22 are associated with the can creels 2.1 and 2.2 on their respective delivery sides. The treatment unit 3 comprises a withdrawal system and draw system as well as additional treatment devices for cutting the tow 14 to the desired staple fibers.

In the schematic arrangement shown in FIG. 1, the cans 13 of the can creel 2.1 are being filled with a tow, whereas the cans 13 of the can creel 2.2 are being emptied, in that the treatment unit 3 withdraws the tows. After all cans 13 in the can creel 2.1 have been filled, and after all cans 13 in the can creel 2.2 have been emptied, the association will be changed. The tow 14 that is withdrawn and treated by the treatment unit 3 is then formed by the tows that are withdrawn from the cans 13 of the can creel 2.1. At the same time, the cans 13 of the can creel 2.2 are filled with the tow 11.

The special advantage of the method according to the invention and the apparatus of the invention lies in particular in a substantially continuous operation of the two process steps with only short times of interruption. In particular the avoidance of costly transportation steps brings considerable savings in time. Furthermore, the can creels 2.1 and 2.2 can be arranged relative to each other, without having to take into account any transportation paths or transportation steps. It is thus possible to provide very compact arrangements of can creels, which directly cooperate with the adjacent or superposed spin unit 1 or with the adjacent or superposed treatment unit 3.

FIGS. 2-4 schematically illustrate different views of a first embodiment of the apparatus according to the invention for carrying out the method of the invention. In this connection, FIG. 2 is a side view of the complete production line, FIG. 3 a front view of the can creels, and FIG. 4 a top view of the can creels. Unless express reference is made to one of the Figures, the following description will apply to all Figures.

To begin with, the general construction of the embodiment of the apparatus according to the invention is shown in greater detail with reference to FIG. 2.

For carrying out a first process step of the method according to the invention, the embodiment comprises a spin unit 1, and for carrying out a second process step, it comprises a treatment unit 3. The spin unit 1 and the treatment unit 3 cooperate with two juxtaposed can creels 2.1 and 2.2.

For melt spinning a tow 11, the spin unit 1 comprises a plurality of spinnerets 6.1-6.3. In the present embodiment, the number of spinnerets is exemplary. Spin units of this type may comprise a plurality of spinnerets. Associated with each spinneret 6.1, 6.2, and 6.3 is a spin pump 5.1, 5.2, and 5.3. The spin pumps 5.1-5.3 connect via a melt distributor 32 to an extruder 4.

The spinnerets 6.1-6.3 are made annular for purposes of extruding a plurality of filaments in a circular arrangement to a filament strand. Downstream of the spinnerets 6.1-6.3, outflow quench devices 7.1-7.3 extend in concentric relationship with respective spinnerets. Each of the outflow quench devices 7.1-7.3 connects to a cooling air supply line (not shown) to generate a cooling air stream for cooling the filament strands.

Downstream of each of the outflow quench devices 7.1-7.3, lubrication devices 8.1-8.3 are provided, each for bundling the filaments. In the direction of the advancing filament strands, a withdrawal system 9 follows downstream of the lubrication devices 8.1-8.3. The withdrawal system 9 comprises a plurality of driven rolls arranged in side-by-side relationship. In the inlet region of the withdrawal system 9, it is preferred to provide lubrication rolls which combine the filament strands 12.1-12.3 to a tow 11.

Arranged downstream of the withdrawal system 9 are rolls, which advance the tow 11 to a depositing device 10.

A guide system 15 supports the depositing device 10 and permits it to be selectively positioned above either of the can creels 2.1 and 2.2. To this end, the spin unit 1 and the can creels 2.1 and 2.2 are arranged in tiers, one on top of the other. The depositing device 10 comprises a conveying means 20 which delivers the tow 11 into a can of the can creel 2.1. The conveying means 20 is coupled with a moving means 19, which causes the conveying means 20 to perform an oscillating pivotal movement. With that, it is possible to deposit the tow 11 evenly over the entire opening cross section of the associated can 13. A depositing device of this type is disclosed, for example, in EP 1 369 370 A2. To this extent, the cited publication is herewith explicitly incorporated by reference, so that a further description may be omitted.

The guide system 15 as well as the arrangement of the can creels 2.1 and 2.2 are described in greater detail in the following.

The tows stored in the cans 13 of the second can creel 2.2 are withdrawn by the treatment unit 3. The treatment unit 3 is generally referred to as a fiber line, and it comprises a plurality of treatment devices for being able to draw and treat the individual tows that have been joined to one tow 14. The setup of the treatment device 3 shown in FIG. 2 is exemplary with respect to the arrangement and number of the treatment devices, and shows only the essential treatment devices that are required for carrying out the second process step.

A draw system 25 removes the tows 11 from the cans 13 of can creel 2.2. In this process, the tows 11 are combined to one tow 14 and advanced over guide rolls 22 and deflection rolls 31. Downstream of the draw system 25 is a crimping device 27. Normally, the crimping device 27 is constructed as a stuffer box crimping mechanism, in which the tow is jammed by a feed means into a stuffer box. As conveying means one could use rolls, for example, in the case of a two-dimensional crimp. The crimping device 27 is followed by a drying device 28, a tension adjusting device 29, and finally a cutting device 30. The use of a drying device depends on the type of the polymer.

To produce the staple fibers, a tow 11 is melt spun in accordance with the arrangement of the embodiment shown in FIG. 2 by means of the spin unit 1 in a first process step. To this end, a thermoplastic plastic is melted by the extruder 4 and supplied to the spin pumps 5.1-5.3. The spin pumps 5.1-5.3 advance the plastic melt under a pressure to the associated spinnerets 6.1-6.3. Each of the spinnerets 6.1-6.3 comprises a plurality of spin holes, so that one filament is extruded from each spin hole. Spinnerets of this type may have as many as several thousand spin holes. From the spinnerets 6.1-6.3, the filaments are jointly removed by the withdrawal device 9. In this process, the filaments are cooled, lubricated, and combined to filament bundles 12.1-12.3. Before entering the withdrawal device 9, the filament bundles 12.1-12.3 are combined to a tow 11. From the withdrawal device 9, the tow 11 advances over a guide roll 21 to the depositing device 10. The depositing device 10 is mounted to the guide system 15, and can be selectively moved to each can 13 within the can creel 2.1. The depositing device is used to advance the tow 11 into a can 13 of the can creel 2.1.

At the same time, the treatment device 3 withdraws the tows of the adjacent can creel 2.2 to perform the second step of the method according to the invention. In this step, the tows 11 that are deposited in the cans 13 of can creel 2.2 are jointly withdrawn by the draw system 25 via the guide rolls 22 and deflection rolls 31, and joined to one tow 14 before entering the draw system 25. The tow 14 advances through the fiber line, and in so doing, it is drawn in the draw system 25. To this end, it is preferred to provide a plurality of heated and also unheated draw rolls 26.

After the drawing step, the tow advances through a setting device (not shown). In this process, one may precede or insert one or more thermal treatments. After the setting step, the tow 14 enters the crimping device 27. Subsequently, the crimped tow 24 advances via the tension adjusting device 29 into the cutting device 30, which cuts the tow 14 to staple fibers of a predetermined length. Thereafter, the produced staple fibers can advance, for example, pneumatically to a baling press for being compacted to a bale. This completes the second process step of the method according to the invention.

To explain the cooperation between the first process step and the second process, the devices for filling and emptying the can creels 2.1 and 2.2 are described in greater detail in the following with reference to FIGS. 3 and 4. The following description will apply to both Figures, unless express reference is made to one of the Figures.

The can creels 2.1 and 2.2 are arranged side by side with a small spacing in between. In this arrangement, the cans 13 are accommodated in the can creel 2.1, and the cans 13 in the can creel 2.2 in two parallel lines side by side. On the upper side of the can creels 2.1 and 2.2, each can is provided with a withdrawal guide element 23 which is mounted to a free end of a pivot arm 24. The withdrawal guide element 23 could be formed, for example, by an eyelet or a roll. The pivot arm 24 is mounted for pivotal movement to the can creels 2.1 and 2.2. The pivot arm 24 permits moving the withdrawal guide element 23 selectively to an idle position on the side next to the can 13 or to an operating position in the center of the can 13. During the filling of a can 13, the pivot arm 24 with the withdrawal guide element 23 is moved to the idle position as shown in the case of can creel 2.1. To withdraw the tows from the cans 13 of the can creel 2.2, all withdrawing guide elements 23 are pivoted with their pivot arms 24 to the operating position as shown in the case of can creel 2.2

For withdrawing the tows 11 from the cans 13 of can creel 2.2, the respective tows are slidingly guided over the withdrawing element 23 and removed by the treatment unit 3.

For filling the cans 13 of can creel 2.1, the depositing device 10 is supported by the guide system 15. In the present embodiment, the guide system is formed by a guide frame 16 that extends over the can creels 2.1 and 2.2. The guide frame 16 mounts a carriage 17 which is adapted for reciprocal movement within the guide frame 16 by a drive (not shown). The carriage 17 is provided with a linear guideway 18 for moving therein a holder 33 of the depositing device 10. The holder 33 can be activated in the linear guideway 18 by a drive (not shown) and be moved transversely to the longitudinal movement of the carriage 17. Thus, by coordinating the movement of the carriage 17 and the movement of the holder 33 in the linear guideway 18, it becomes possible to move the depositing device 10 to each can 13 of the can creel 2.1 or 2.2.

The holder 33 mounts a conveying means 20 in the form of two reels. These reels are adapted for performing an oscillating pivotal movement transversely to the direction of movement of the holder 33 by means of the moving means 19 that may be formed by a pivotal support. A conveying means of this type with a pivotal support is disclosed in EP 1 369 370 A2, so that for a description in greater detail the cited publication is herewith incorporated by reference.

For depositing a tow, the conveying means 20 and the holder 33 are caused to perform an oscillating movement within a filling cross section above the can 13. This makes it possible to attain a uniform deposit of the tow 11 in every region of the can.

Upstream of the conveying means 20 is a feed system 21 that advances the tow 11 to the conveying means 20. Preferably, the feed system 21 comprises a plurality of driven rolls. With that, it is possible to attain an adequate tension in the tow regardless of the travel of the depositing device 10.

The depositing device 10 shown in FIGS. 2-4 is only exemplary, and shows a possibility of depositing a tow into a can 13. In principle, the depositing device could be formed by stationary conveying means 20, to which one would associate an additional guide means that is adapted for oscillating movement to deposit the tow into the can. However, it is also possible to combine a depositing device 10 with a can traverse mechanism. In this case, the conveying means 20 could also be made immobile. For filling, the can would then perform an oscillating movement in the can creel.

However, it is basically possible to use all devices that are suited to perform a movement of the conveying means for guiding the tow while advancing it, in such a manner that a can is evenly filled with a great filling density.

In their construction and arrangement, the embodiments shown in FIGS. 1-4 are exemplary. In particular, the embodiment of FIG. 4 may be constructed with additional treatment means as well as similar constructional variants. The invention encompasses all apparatus and methods for producing staple fibers, wherein tows formed from a plurality of filament strands are deposited into a can of a can creel for temporary storage between a first process step and a second process step. 

1. A method of producing staple fibers, comprising the steps of forming a tow of melt spun filaments, successively depositing the tow into each of a plurality of cans accommodated in a can creel, and withdrawing the tow from the cans of the can creel and treating and cutting the withdrawn tow.
 2. The method of claim 1, wherein the withdrawing step is conducted after the tow has been deposited into all of the cans of the can creel and while the tow is successively deposited into each of the cans accommodated in a second can creel.
 3. A method of producing staple fibers, comprising the steps of forming a tow of melt spun filament strands, alternately (1) successively depositing the tow into each of a plurality of cans accommodated in a first can creel, and (2) successively depositing the tow into each of a plurality of cans accommodated in a second can creel, and withdrawing the tow from the cans of the second can creel while the tow is deposited in the cans of the first can creel, and withdrawing the tow from the cans of the first can creel while the tow is deposited in the cans of the second can creel.
 4. The method of claim 3, wherein the tow is deposited by a movable depositing device into each can that is to be filled, with the depositing device being supported above the associated can creel.
 5. The method of claim 4, wherein during the depositing step, an oscillating movement is imparted to the tow by the depositing device.
 6. The method of claim 5, wherein the oscillating movement of the tow is generated by a movably mounted conveying means.
 7. The method of claim 3, wherein during each of the depositing steps, the can receiving the tow performs an oscillating movement in the can creel.
 8. An apparatus for producing staple fibers, comprising a melt spinning unit for melt spinning a plurality of filaments and gathering the filaments to form a tow, a depositing device for successively depositing the tow into each of a plurality of cans which are accommodated in a can creel, and a treatment unit for withdrawing the tow from the cans of the can creel and treating and cutting the withdrawn tow.
 9. The apparatus of claim 8, further comprising a second can creel arranged adjacent the first mentioned can creel, and wherein both can creels are arranged relative to the melt spinning unit such that the cans of the two can creels can be alternately filled with the tow.
 10. The apparatus of claim 9, wherein the two can creels are arranged relative to the treatment unit such that the tows of the cans of the two can creels can be alternately withdrawn.
 11. The apparatus of claim 10, wherein the melt spinning unit comprises a movable depositing device which is supported and moved by a guide system which is supported above the can creels.
 12. The apparatus of claim 11, further comprising a moving means which causes the depositing device to perform an oscillating movement while depositing the tow.
 13. The apparatus of claim 12, wherein the moving means is associated with a conveying means which is adapted for advancing the tow into the respectively associated can.
 14. The apparatus of claim 10, further comprising a can traversing mechanism for imparting oscillating movement to the cans of each of the can creels while the tow is deposited thereinto.
 15. The apparatus of claim 8, wherein the melt spinning unit comprises a plurality of spinnerets for extruding a plurality of filaments and a withdrawal system for withdrawing and gathering the filaments from the spinnerets to form a tow which is advanced to the depositing device.
 16. The apparatus of claim 15, further comprising a feed system for advancing the tow from the withdrawal system to the depositing device.
 17. The apparatus of claim 16, wherein the spinnerets and the withdrawal system of the melt spinning unit are arranged upstream of the can creels, with the spinnerets being mounted in centered relationship with the can creels or in offset relationship with the can creels.
 18. The apparatus of claim 10, further comprising a withdrawal guide element associated with each can of the can creels and with each withdrawal guide element being adapted for movement between an idle position and an operating position where it serves to facilitate the withdrawal of the tow from the cans. 